In musical instruments having substantial tonal resources, it is frequently necessary to effect elaborate changes in the values of various controls used to define the tonal resources in times of the order of 0.2 second with as little effort on the player's part as possible, even though dozens of parameters must be redefined. As pointed out by Melville Clark in a PROPOSED KEYBOARD MUSICAL INSTRUMENT, J. Acoust. Soc. Am., 31, 403-419 (1959), FIGS. 17 and 18 particularly or U.S. Pat. No. 3,120,636, these changes can be effected with a finger bar that runs parallel to and that is placed between the manuals of a multimanual instrument and by another toe bar that runs parallel to the pedal clavier and just above the front thereof. Depression of any one of the bars causes the next preselected combination to appear essentially instantly. To this end, only a single finger or the toe of either foot need be used; this actuation can be accomplished without removing either hand from its respective keyboard or either foot from the pedalboard. It was further pointed out in the references cited that with differential control, the values of any of the parameters could be readjusted by the player anytime after the depression of any bar without disturbing the system.
Before a composition is played the values of many parameters can and should be settled upon. The tone colors to be used for each musical element at each stage of the composition, the degree of choral massiveness, and the apparent location and size of the sound source are among these parameters that should and can be preselected before a composition is played. These values are stored in a memory and brought into action in sequence upon depressing any of the bars.